/Engine/Source/Runtime/Engine/Public/Blueprint/BlueprintExtension.h
Per-instance extension object that can be added toUBlueprint::Extensionsin order to augment built-in blueprint functionality Ideally this would be an editor-only class, but such classes are not permitted within Engine modules (even inside WITH_EDITORONLY_DATA blocks)
class UBlueprintExtension : public [UObject](API\Runtime\CoreUObject\UObject\UObject)